This invention relates to high expansion cobalt-chrome-based dental alloys.
Gold-based alloys in dentistry were initially replaced by more economical palladium-based alloys. Recent increases in the price of palladium are making these alloys very expensive. Other economical alternatives have been nickel-based, cobalt-based and titanium-based systems. Nickel-based alloys allegedly have sensitivity and toxicity concerns. Titanium-based alloys are difficult to process and require special care and expensive equipment. These alloys, while being thermally compatible with conventional porcelains are not compatible with many high expansion porcelains available today. Although gold-based alloys are being marketed for use with high expansion porcelains, no economical alternatives exist. Metal free ceramic/composite systems and sintered or plated copings have also been used, but may lack the strength and other properties inherent in metals and alloys which render metals and alloys more desirable than their ceramic counterparts.
Thus, there is need for developing non-allergenic cobalt-based alloys to fill this void that exhibit many of the properties of precious metal alloys heretofore considered desirable in the fabrication of porcelain-veneered bridgework and crowns.
These and other objects and advantages are accomplished by the present invention which provides chromium-cobalt alloys which are significantly different from chromium-cobalt alloys heretofore employed in the fabrication of prosthetic dental appliances. The alloys herein exhibit greatly improved oxidation resistance thereby facilitating the formation of a tenacious bond with high-expansion porcelain. The alloys herein comprise cobalt, chromium and manganese as essential components and include one or more of aluminum, indium, gallium, tin, and germanium, and may include one or more of iron, nickel, palladium and platinum. Optional components include gold, tantalum, niobium, molybdenum, tungsten, vanadium, iridium, ruthenium, rhenium, titanium, silicon, copper, zirconium, hafnium, boron, yttrium, and rare earths metals. The alloys herein are useful with high-expansion dental ceramics and porcelains, most preferably with those recently introduced to the market in the range of about range from 14 to 18.5xc3x9710xe2x88x926.